Continuously variable transmissions (CVTs) present many advantages over the conventional automatic step gear transmission including efficiency gains and a reduction in mechanical complexity. The continuously variable transmission may utilize a torque converter and neutral idle and garage shift features. Transmission fluid can be used to fluidly couple various components of the CVT.
Multiplex devices, similar to a modified conventional combination of valve assemblies, may be used in the continuously variable transmission to route the transmission fluid to various components. An exemplary implementation of a multiplex device is illustrated in FIGS. 1, 2A, 2B, 3A, and 3B, where an exemplary multiplex device transmission control is generally indicated by reference numeral 10. The transmission control system 10 includes a multiplex device 12, which is supplied the transmission fluid at a controllable pressure by a transmission pump 14. It should be appreciated that the multiplex device 12 may be indirectly connected to the transmission pump 14 and this connection may vary considerably between transmission configurations. Furthermore, the multiplex device 12 directs transmission fluid to other components of the transmission control system 10 but does not attenuate the pressure of the transmission fluid beyond typical mechanical losses.
The multiplex device 12 is further connected to a multiplex control 16, which selectively switches the multiplex device 12 between an on position 12a (shown in FIGS. 2A and 2B) and an off position 12b (shown in FIGS. 3A and 3B). The multiplex device 12 selectively delivers transmission fluid through four delivery paths. The first path is indicated by reference numeral 18. The second, third, and fourth path are indicated by reference numerals 20, 22, and 24, respectively. It will be appreciated that the multiplex device 12 utilizes two of the four delivery paths in one position and then utilizes the other two delivery paths in the other position. For example, the multiplex device 12 in the on position 12a (FIGS. 2A and 2B) communicates fluid through the first delivery path 18 and third delivery path 22. The multiplex device 12 in the off position 12b (FIGS. 3A and 3B) communicates fluid through the second delivery path 20 and the fourth delivery path 24.
The NI/GS control valve 26 is actuated by a dual valve control 28, which also actuates a torque converter clutch (TCC) control valve 30. The dual control valve 28 is configured to actuate the NI/GS control valve 26 in a way opposite the TCC control valve 30. More specifically, when the dual control valve 28 opens the NI/GS control valve 26 to a maximum position, the dual control valve 28 controls the TCC control valve 30 to a minimum position. When the dual control valve 28 controls the NI/GS control valve 26 to a minimum position, the dual control valve 28 opens the TCC control valve 30 to a maximum position. The maximum position, with respect to the NI/GS control valve 26 and the TCC control valve 30, is defined as allowing maximum flow through the valves 26 and 30, which necessarily means the fluid pressure is not attenuated as it travels from transmission pump 14 though the multiplex device 12 to the valves 26 and 30 except for typical mechanical losses. The minimum position, on the other hand, is defined as reducing or attenuating the pressure of the transmission fluid as it travels through the valves 26 and 30 when compared to the transmission fluid pressure experienced at the multiplexer device 12.
The NI/GS control valve 26 is fluidly connected to a forward/reverse clutch 32, which directs the transmission fluid to either a modified conventional forward clutch 34 or a modified conventional reverse clutch 36. The forward clutch 34 and the reverse clutch 36 are components of the transmission 38, which are connected to an engine 40. When the transmission fluid is directed to the NI/GS control valve 26 that is in the maximum position, the forward/reverse valve 32 routes transmission fluid at a maximum pressure from the NI/GS Control Valve 26 to either the forward clutch 34 or the reverse clutch 36. When the transmission fluid is directed to the NI/GS control valve 26 that is in the minimum position, the forward/reverse valve 32 routes transmission fluid at a minimum pressure from the NI/GS Control Valve 26 to either the forward clutch 34 or the reverse clutch 36. When either the forward clutch 34 or the reverse clutch 36 receives transmission fluid at a maximum pressure, either the forward clutch 34 or the reverse clutch 36 locks. In contrast, when either the forward clutch 34 or the reverse clutch 36 receives transmission fluid at a minimum pressure, either the forward clutch 34 or the reverse clutch 36 opens.
Maximum pressure is defined as the transmission fluid pressure at a certain point within the control system 10 being about equal to the transmission fluid pressure experienced at the multiplexer device 12, acknowledging typical mechanical losses. Minimum pressure is defined as the transmission fluid pressure at a certain point within the transmission control system 10 being reduced, when compared to the transmission fluid pressure experienced at the multiplexer device 12. In the various embodiments, maximum transmission fluid pressure is about 290 psi (about 2000 kPa) and minimum fluid pressure is about 0.3 psi (about 2 kPa). Minimum pressure further refers to an adequate amount of transmission fluid pressure required to cool and maintain the particular component in the transmission but not necessarily control it.
The TCC control valve 30 is fluidly connected to a modified conventional torque converter clutch 42 (TCC 42). The TCC 42 is a component of the transmission 38, which is connected to an engine 40. When the transmission fluid is directed to the TCC Control Valve 30 that is in the maximum position, the TCC 42 receives transmission fluid at a maximum pressure from the TCC Control Valve 30. It follows that when the TCC control valve 30 that is in the minimum position, the TCC 42 receives transmission fluid at a minimum pressure from the TCC Control Valve 30. When the TCC 42 receives transmission fluid at a maximum pressure, the TCC 42 locks. A locked TCC 42 causes a torque converter (not shown) that is conventionally connected to the transmission 38 to lock, which means the torque converter does not slip or experiences very little slippage. In contrast, when the TCC 42 receives transmission fluid at a minimum pressure, TCC 42 opens, which causes the torque converter to slip.
Table 1 below indicates the various positions of the components of the transmission control system 10, shown in seven exemplary modes. Each mode represents possible exemplary configurations associated with the multiplex drive 12, the NI-GS control valve 26, the forward-reverse valve 32, the forward clutch 34, and the reverse clutch 36. The labels of Maximum and Minimum in the column labeled NI-GS control valve 26 are in reference to the definitions noted above. Bypassed is defined to mean that the transmission fluid does not flow to this component. As shown in FIG. 2, for example, when the multiplex device 12 is in the on position 12a, no transmission fluid flows to the NI-GS control valve 26. As such, the NI-GS control valve 26 is bypassed, as the transmission fluid flows directly from the multiplex device 12 to the forward/reverse clutch 32.
TABLE 1NI-GSMultiplexcontrolforward-reverseforwardreverseModesDevicevalve (26)valve (32)clutch (34)clutch (36)0OffN/ANo ForwardOpenOpenPositionNo Reverse1OffMaximumForwardLockedOpenPosition2OffMaximumReverseOpenLockedPosition3OffMinimumForwardOpenOpenPosition4OffMinimumReverseOpenOpenPosition5OnBypassedForwardLockedOpenPositionMinimum6OnBypassedForwardLockedOpenPositionMaximum
Table 2 below indicates the various positions of the components of the transmission control system 10, shown in the same seven different modes. Each mode represents possible exemplary configurations associated with the multiplex device 12, the TCC control valve 30, and the TCC 42. The labels of Maximum and Minimum in the column labeled TCC control valve 30 are in reference to the definitions noted above. Bypassed is defined to mean that the transmission fluid does not flow to this component. As shown in FIG. 3, for example, when the multiplex device 12 is in the off position 12a, no transmission fluid flows to the TCC control valve 30. As such, the TCC control valve 30 is bypassed, as the transmission fluid flows directly from the multiplex device 12 to the TCC 42.
MultiplexTCC controlModesDevice (12)valve (30)TCC (42)0Off PositionBypassedOpenMinimum1Off PositionBypassedOpenMinimum2Off PositionBypassedOpenMaximum3Off PositionBypassedOpenMaximum4Off PositionBypassedOpenMaximum5On PositionMinimumOpen6On PositionMinimumOpen
With reference to FIGS. 3A and 3B and Tables 1 and 2, the multiplex device 12 is shown in the off position 12b. Modes 1-4 in Tables 1 and 2 indicated possible configurations of the components of the transmission control system 10. Mode 1 refers to the multiplex device 12 in the off position 12b, the forward-reverse valve 32 in a forward position 32a (FIG. 3A), and the NI-GS control valve 26 in a maximum position. Mode 2 is identical to Mode 1 except the forward-reverse valve 32 is in a reverse position 32b (FIG. 3B). In mode 1 and 2, there is no transmission fluid directed though the first and the third delivery path 18 and 22 and, therefore, no transmission fluid is directed to the TCC control valve 30. Because the TCC control valve 30 is bypassed, transmission fluid is delivered directly from the multiplex device 12 at a minimum pressure to the TCC 42. Because transmission fluid is directed to the NI-GS Control Valve 26 and then to either the forward clutch 34 or reverse clutch 36 (depending on the position of the forward/reverse valve 32), the NI-GS control valve 26 is able to regulate either the forward clutch 34 or reverse clutch 36 accordingly.
Mode 3 is identical to Mode 1 and Mode 4 is identical to Mode 2 except the NI-GS control valve 26 is in a minimum position in Mode 3 and Mode 4 . Because transmission fluid is directed to the NI-GS control valve 26 set to the minimum pressure, either the forward clutch 34 or reverse clutch 36 (depending on the position of the forward/reverse valve 32) will remain open. It will be appreciated that when the NI-GS control valve 26 moves from the maximum position to the minimum position, the TCC control valve 30 moves from the minimum position to the maximum position because the dual control valve 28 controls control the two valves 26 and 30 oppositely.
With reference to FIGS. 2A and 2B and Tables 1 and 2, the multiplex device 12 is shown in the on position 12a. Modes 5 and 6 in Tables 1 and 2 indicated possible configurations of the components of the transmission control system 10. Mode 5 refers to the multiplex device 12 in the on position 12a, the forward-reverse valve 32 in a forward position 32a (FIG. 2A), and the NI-GS control valve 26 in a maximum position. In mode 5, there is no transmission fluid directed though the second and the fourth delivery path 20 and 24 and, therefore, no transmission fluid is directed to the NI-GS control valve 26. Because the NI-GS control valve 26 is bypassed, transmission fluid is delivered directly from the multiplex device 12 at a maximum pressure to the forward/reverse valve 32. Because transmission fluid is directed to the TCC control valve 30 and then to the TCC 42, the TCC Control Valve 30 is able to open or close the TCC 42 accordingly.
Mode 6 is identical to Mode 5 except the TCC control valve 30 is in a minimum position in Mode 6. Because transmission fluid is directed to the TCC control valve 30 set to the minimum pressure, the TCC 42 will remain open. It will be appreciated that when the TCC control valve 30 moves from the maximum position to the minimum position, the NI-GS Control Valve 26 moves from the minimum position to the maximum position because the dual control valve 28 controls control the two valves 26 and 30 oppositely.
A neutral-idle feature may be incorporated into an automatic transmission. In this example, a vehicle (not shown) comes to a stop. After a pre-determined period of time, the automatic transmission may initiate the neutral idle feature. More specifically, while waiting at the stop a driver may have the vehicle in a forward gear with a brake pedal pressed so that the vehicle is in gear but stopped. At this point, the transmission control system 10 may be in Mode 1; such that, the forward clutch 34 is locked and the TCC 42 is open. In this case, if the driver were to release the brake the vehicle would move forward, as the vehicle remains in gear even though the vehicle is stopped. To increase the efficiency of the engine 40, the transmission control system 10 may open the forward clutch 34 thus removing the load on the engine 40, which in turn may reduce fuel consumption and increase engine and transmission life.
To open the forward clutch, the multiplex device 12 must be in the off position 12b (FIGS. 3A and 3B) and the NI/GS control valve 26 must be in the minimum position. Because the NI/GS control valve 26 and the TCC control valve 30 are controlled by the same dual control valve 28, the TCC control valve 30 will be in the maximum position when the NI/GS control valve 26 is in the minimum position. If the multiplex device 12, however, is stuck in the on position 12a (FIGS. 2A and 2B), and the transmission control system 10 initiates the neutral idle feature, there is a possibility that the engine 40 will stall. More specifically, the NI/GS control valve 26 will still move from the maximum position to the minimum position in the attempt to unlock the forward clutch 34, which in turn forces the TCC control valve 30 from the minimum position to the maximum position. The multiplex device 12, however, is stuck in the on position 12a (FIGS. 2A and 2B) and transmission fluid is directed to the TCC control valve now in the maximum position. This scenario results in the forward clutch 34 being locked and the TCC 42 switching from open to being locked. If this scenario occurs, the engine 40 may stall.
A garage-shift feature may also be incorporated into an automatic transmission. In this example, a vehicle (not shown) comes to a stop and places the automatic transmission in either neutral or park. At this point, the automatic transmission may initiate the garage-shift feature. More specifically, the driver will either turn the ignition off or place the automatic transmission back into a forward or reverse drive gear to continue driving. Upon placing the automatic transmission back into a drive gear from either park or neutral, the automatic transmission will slowly engage the forward or reverse clutch accordingly to provide a smooth transition from stopped to forward or reverse motion. Not using the garage-shift feature may result in less attenuated or less smooth transition to forward or reverse motion from a stand still.
When the vehicle is parked and the automatic transmission is in either park or neutral, the transmission control system 10 is in Mode 0; such that, the multiplex device 12 is in the off position (FIG. 3A), the forward clutch 34 and the reverse clutch 36 are open, and the TCC 42 is open. Now when the driver shifts into a drive gear, the forward clutch 34 or reverse clutch 36 is slowly closed, to provide a gradual transition to forward or reverse motion. To slowly close the forward or reverse clutch, the multiplex device 12 must be in the off position 12b (FIGS. 3A and 3B) and the NI/GS control valve 26 must be moved from the minimum position to the maximum position. Because the NI/GS control valve 26 and the TCC control valve 30 are controlled by the same dual control valve 28, the TCC control valve will be move from the minimum position to the maximum position when the NI/GS control valve 26 moves to the minimum position.
If the multiplex device 12, however, is stuck in the on position 12a (FIGS. 2A and 2B), and the transmission control system 10 initiates the garage shift feature, there is a possibility that the engine 40 will stall. More specifically, the NI/GS control valve 26 will still move from the minimum position to the maximum position in the attempt to gradually lock the forward clutch 34 or reverse clutch 36. The forward clutch 34 or reverse clutch 36 must open first, which requires the NI/GS control valve 26 to move from a maximum position to a minimum position. The TCC control valve 30, therefore, moves from the minimum position to the maximum position. If, however, the multiplex device 12 is stuck in the on position 12a (FIGS. 2A and 2B) and transmission fluid is directed to the TCC control valve now in the maximum position. This scenario results in the forward clutch 34 or reverse clutch 36 being locked and the TCC 42 switching from open to being locked. If this scenario occurs when the vehicle is at a stand still the engine may stall.
In some instances, as noted above, the multiplex device 12 remains stuck in an on position when otherwise commanded to return to the off position. This failure, if gone undetected, may cause engine stall. Previous implementations of the multiplex device diagnostic to detect the multiplex device stuck in the on position have been limited to running the diagnostic only when the vehicle is in a park or neutral range. Further, the previous diagnostic was limited to transmission temperatures below 80° C.